Refractive errors such as myopia, hyperopia, and astigmatism affect a large segment of the population irrespective of age, sex and ethnic group. If uncorrected, such errors can lead to impaired quality of life. One method to determine the visual acuity of a person is to use a phoropter to do a subjective vision test (e.g. blur test) which relies on feedback from the subject. The phoropter is used to determine the refractive power needed to bring any projected image to focus sharply onto the retina. A traditional phoropter is usually coupled with a screen or a chart where optotypes are presented, for example a Snellen chart. A patient is asked to look through the instrument to a chart placed at optical infinity, typically equivalent to 6 m/20 feet. Then he/she will be asked about the letters/symbols presented on the screen, and whether he/she is able to differentiate/resolve the letters. The patient will keep looking at letters of smaller size or higher resolution power until there is no improvement, at that time the eye-care practitioner is able to determine the visual acuity (VA) of the subject and proceed with the other eye.
Light field displays are known to adjust a user's perception of an input image by adjusting a light field emanated by the display so to control how a light field image is ultimately projected for viewing. For instance, in some examples, users who would otherwise require corrective eyewear such as glasses or contact lenses, or again bifocals, may consume images produced by such devices in clear or improved focus without the use of such eyewear. Other light field display applications, such as 3D displays, are also known.
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